Our research focuses on the development and use of animal model systems to study the regulation of gastrointestinal functions. Of particular concern are the regulation of intestinal absorption and metabolism of nutrients, and alteration of these occurring in response to oral exposure to biologically active environmental toxins. Current examples of these studies are: 1) the intestinal assimilation of nutrients in normal and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) treated animals. The physiologic mechanisms of process regulation developed in these studies rely on in vitro and in vivo techniques; 2) the differentiation of intestinal cell and subcellular proteins; and 3) the role of NAD-linked dehydrogenases, for example, NAD-linked L-glycerol-3-phosphate dehydrogenase (NAD-2-GPDH), in the energy metabolism of the normal colon and 1,2-dimethylhydrazine-induced colon tumor.